CN101569116B - Method and apparatus to support SDMA transmission in OFDMA based network - Google Patents

Method and apparatus to support SDMA transmission in OFDMA based network Download PDF

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CN101569116B
CN101569116B CN2007800482869A CN200780048286A CN101569116B CN 101569116 B CN101569116 B CN 101569116B CN 2007800482869 A CN2007800482869 A CN 2007800482869A CN 200780048286 A CN200780048286 A CN 200780048286A CN 101569116 B CN101569116 B CN 101569116B
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excited users
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CN101569116A (en
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A·多尔
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Intel Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/30—TPC using constraints in the total amount of available transmission power
    • H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
    • H04W52/346—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading distributing total power among users or channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0014—Three-dimensional division
    • H04L5/0023—Time-frequency-space
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0037—Inter-user or inter-terminal allocation
    • H04L5/0039—Frequency-contiguous, i.e. with no allocation of frequencies for one user or terminal between the frequencies allocated to another
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/0064—Rate requirement of the data, e.g. scalable bandwidth, data priority
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/02—Channels characterised by the type of signal
    • H04L5/023—Multiplexing of multicarrier modulation signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/28—Cell structures using beam steering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

Techniques are provided for efficiently optimizing scheduling and beamforming in an OFDMA-based wireless network that uses SDMA. The techniques are capable of achieving a high level of spectral efficiency and throughput in a low complexity manner while still addressing quality of service (QoS) constraints.

Description

For support the method and apparatus of SDMA transmission at the network based on OFDMA
Technical field
Put it briefly, the present invention relates to radio communication, specifically, relate to the system of other technology of using OFDM (OFDMA) or relevant a plurality of parallel channels.
Background technology
OFDM (OFDM) is the quadrature carrier that uses a large amount of tight spacings, sends the multi-carrier communication technology of data by communication channel.OFDM (OFDMA) is a kind of OFDM form that makes a plurality of users share subcarrier on the OFDM frequency band.Space division multiple access (SDMA) is a kind of for example, by utilizing Spatial Dimension to make the technology of a plurality of user's shared communication resources (, frequency channels etc.).Need for realize efficiently the technology of SDMA in the OFDMA system.
The accompanying drawing explanation
Fig. 1 is according to embodiments of the invention, shows the diagram of spendable exemplary OFDM symbol in the network based on OFDMA;
Fig. 2 is according to embodiments of the invention, shows in wireless network by using the block diagram that beam forming (BF) can the example that separate implementation space between antenna beam;
Fig. 3 is according to embodiments of the invention, shows for the network based on OFDMA and selects user's subgroup to share the flow chart of the illustrative methods of the first subchannel;
Fig. 4 is according to embodiments of the invention, shows the flow chart of selecting the illustrative methods of a plurality of excited users group for a plurality of parallel channels in communication network;
Fig. 5 and 6 is according to embodiments of the invention, shows the part of the flow chart of the illustrative methods for carrying out beam forming optimization;
Fig. 7 is according to embodiments of the invention, shows the block diagram of exemplary base.
Embodiment
In the following detailed description, with reference to accompanying drawing, wherein, accompanying drawing shows for carrying out specific embodiments of the invention by example.Those skilled in the art fully described these embodiment in detail, so that can carry out the present invention.Although should be appreciated that the various embodiments of the present invention difference, they are without being mutual exclusion.For example, special characteristic, structure or the characteristic relevant with embodiment as herein described can realize can breaking away from the spirit and scope of the present invention in other embodiments and not.In addition, should be appreciated that in each the disclosed embodiments, can revise the position of individual component and arrangement and can not break away from the spirit and scope of the present invention.Therefore following detailed description is not restrictive, and scope of the present invention is only that the four corner of the equivalent of being authorized by appended claims and the claim of appropriate explanation is defined.In the accompanying drawings, in a plurality of figure, identical Reference numeral refers to same or similar function.
OFDM is used a plurality of orthogonal sub-carriers, carrys out the multi-carrier communication technology of transmission of information by communication channel.Can modulate each subcarrier with different data symbols.All modulated sub-carriers can be transmitted as single " OFDM symbol " together.Can pass through channel transmission OFDM symbol one by one, to realize high data rate communication.In traditional OFDM method, each OFDM symbol that base station (BS) transmits mails to unique user (for example, the unique user station (SS) in the overlay area of BS).That is,, if used the total data subcarrier of OFDM symbol, the total data subcarrier of OFDM symbol carries the information for unique user so.OFDM access (OFDMA) is the expansion of OFDM, and it allows to distribute the subcarrier of OFDM frequency band between different in a large number users.Therefore, when BS sends the OFDM symbol in the network based on OFDMA, some subcarriers in the OFDM symbol can carry the data of first user, and some subcarriers can carry the second user's data etc.Similarly, when BS receives the OFDM symbol in the network based on OFDMA, some subcarriers that receive can carry the data from first user, and some subcarriers can carry from data of the second user etc.Scheduler can be provided in BS, to determine when and in which subcarrier, data to be sent to independent SS from BS, and determine when and in which subcarrier, data sent to BS from independent SS.This information communicates with corresponding SS according to the form of the MAP data that sent by BS.
In typical OFDMA configuration, the OFDM frequency band division is become to large quantum channel, every sub-channels comprises one or more subcarriers.Scheduler can be distributed to different users by the every sub-channels in the OFDM symbol.The user who is assigned to each subchannel can also change in time.For example, in an OFDM symbol, the first subchannel can be distributed to user A, and in follow-up OFDM symbol, the first subchannel be distributed to user D etc.
SDMA utilizes spatial separation between antenna beam to allow the technology of a plurality of user's shared communication resources.While in the system based on OFDMA, using SDMA, by generating separated antenna beam on the space for a plurality of users, these users can share the every sub-channels in the OFDM bandwidth.Fig. 1 is according to embodiments of the invention, shows the figure of the exemplary OFDM symbol 10 that can use in the system based on OFDMA.As shown in the figure, OFDM symbol 10 comprises a plurality of subcarriers 12.Great majority in these subcarriers 12 are can carry to mail to and from the data subcarrier of each user's user data.But some subcarriers 12 can be pilot sub-carriers, it can be used for impelling the channel estimating in network for example.Subcarrier 12 is divided into to a plurality of subchannels (that is, subchannel 1,2,3...N), and every sub-channels can comprise one or more subcarriers.In shown embodiment, every sub-channels is distributed to a plurality of users and use.That is, subchannel 1 being distributed to subscriber station (SS) A, SS D and SS F uses; Subchannel 2 is distributed to SS C, SS F and SS H use etc.The reason that a plurality of users can share every sub-channels is because the transmission of having used beam forming technique spatially will carry out (using SDMA) each user of shared every sub-channels is separated.
Fig. 2 is according to embodiments of the invention, and showing can be by using beam forming (BF) technology to carry out the block diagram of the exemplary network configuration 14 that separate implementation space between antenna beam in wireless network.As shown in the figure, BS 16 provides communication service to a large amount of SS 18,20,22,24,26 in respective coverage areas Yu Huo community.BS 16 has a plurality of antennas 34, and it can be used for impelling the radio communication with SS 18,20,22,24,26.By utilizing a plurality of antennas 34 to use beam forming technique, can generate a plurality of different antenna beams for every sub-channels of OFDM symbol, they are spatially separate.Because wave beam is spatially separated, so will cause to the SS in another wave beam very little interference or not cause interference from the transmission of BS 16 in one of these wave beams.Similarly, in BS 16 receives from particular beam during the transmission of one of a plurality of SS, the transmission from other wave beam that this transmission and BS 16 can be received is separated.For example, with reference to Fig. 2, because each in SS A 18, SS D 20 and SS F 22 is to be served by wave beam 28,30 and 32 separately, so these unit can the shared Sub channel, wherein, each wave beam in wave beam 28,30 and 32 is spatially separated with the wave beam of other two unit of service.Can use similar configuration in each of other available subchannels of OFDMA system.
The linear wave beam shaping is a kind of mode that has the wave beam of desired characteristic by generation, weight coefficient is applied to the technology of each antenna in a plurality of antennas.In the base station with n transmitting antenna, antenna weight can be expressed as to the vector that length is n, it comprises the weight coefficient for each antenna.Available by the standardization of BF vector, wherein, initial norm (Original norm) is the distribution power of wave beam.In typical SDMA situation, the Signal Interference and Noise Ratio (SINR) of the flat fading channel that user k can be experienced is expressed as:
SINR k = p k | v k h k * | 2 σ k 2 + Σ j ≠ i p j | v j h k * | 2
Wherein, v kthe BF vector relevant to user k, h kthe channel vector relevant to user k, p kthe power level relevant to user k, σ k 2the noise relevant to user k (thermal noise and from the interference of neighbor cell).Subtend duration set { v is wanted in SDMA optimization usually iand power set { p imake wise selection.But, in actual multi-user ofdma system, SDMA optimization also is limited by the scheduling requirement.That is, user's speed must meet specific service quality (QoS) constraint.Only the optimized algorithm relevant to throughput can't provide the QoS reached an agreement grade for various users usually.
The present invention relates to, at the SDMA/OFDMA environment, strengthening throughput and spectrum efficiency, also solve the technology of QoS problem simultaneously.The technology that strengthens throughput with relatively low computation complexity also is provided.In at least one embodiment, use a kind of two stage method.In the first stage, for each available subchannels in network's coverage area is selected little user's subgroup.In this article this subgroup is called " the activation group " of subchannel.In second stage, scheduling and the physical wave beam shaping of this overlay area carried out to combined optimization.Combined optimization is a kind of iterative process, and it repeats to adjust various users' power level according to rate constraint, the beam forming of the subchannel that then optimizing user power has been modified again.In many cases, by combined optimization, before the stage, carrying out the first stage, can only with very little performance loss, reduce the overall computation complexity of optimizing process considerablely.Can also carry out the combined optimization stage in the situation that at first do not carry out the subgroup choice phase.
Fixed, BF based on linear predictive coding optimize can realize with the OFDM/SDMA broadcast environment in the throughput that is close of the theoretical limit of throughput.But, when by this optimisation technique, processing a large number of users, operation complexity usually is increased to and exceeds the actual central level of carrying out in real time.For example, during the number of users K in overlay area relatively large (, K=10 to 30), the quantity that emulation demonstrates the user who has positive at the end of BF optimizing process seldom surpasses the quantity n of the antenna for base station used.In practice, the quantity of the antenna in base station is limited in relatively low quantity (for example,, 2-4) usually.Based on aforementioned content, confirmable, by reduced the quantity of the excited users relevant to every sub-channels before carrying out final BF optimization, can significantly reduce overall complexity.
In the following discussion, described activation group prediction (ASP) process, it is used under the prerequisite of not considering the QoS constraint selects for example, user's activation group for given bandwidth resources (, OFDMA subchannel).The ASP process is a kind of low complex degree iterative program, and it found out little high yield (high yield) activation group before BF optimizes.In at least one embodiment, make number of users in each activation group equal the quantity n of the antenna that uses base station.In other embodiments, can use the excited users of other quantity.For example, one or more wireless standards can be limited (for example, IEEE 802.16e standard is 4 by this restricted number) to user's the quantity that obtains service on single resource.
Fig. 3 is according to embodiments of the invention, shows for the network based on OFDMA and selects user's subgroup to carry out the flow chart of the illustrative methods 40 of shared Sub channel.Method 40 is examples of aforesaid activation group prediction (ASP) process.As shown in the figure, at first whole K active user is elected to be to the candidate user (square frame 42) for the first subchannel.Then give all candidate user (square frame 44) for the first subchannel by equal power division.Next each in these candidate user is carried out to the calculating (square frame 46) of performance index (performance metric).In at least one embodiment, performance index relevant to candidate user " speed ", wherein, calculate to maximize this speed by the best to this user (standardized) beam vectors.Distribute to carry out beam vectors optimization based on current candidate set and current power.
Next performance index based on calculated, reduce the quantity (square frame 48) of the candidate user relevant to the first subchannel.If performance index are speed as above, can there is the candidate user of minimum speed limit and the candidate user that reservation has flank speed by rejecting so, reduce the quantity of candidate user.Can specify the degree of minimizing according to any one in multiple distinct methods.For example, in a kind of feasible method, the size of new candidate set can be the constant ratio of the size of former candidate set (for example, 50% etc.).Can also use for reducing other strategy of candidate set size.Next can determine: whether the size of the new candidate set of the first subchannel is desired size (square frame 50).If not yet reach desired size, method 40 can be got back to square frame 44 so, and gives all candidate user in new candidate set by equal power division.Then, the performance index of candidate user in new candidate set are calculated to (square frame 46), and, based on performance index, will again be reduced the quantity (square frame 48) of candidate user.Then, repeat this process until reach the desired size (square frame 50-Y) of candidate set, now method 40 finishes (square frame 52).In at least one embodiment, the minimizing in square frame 48 can not reduce to the quantity of candidate user under desired number of users.
When using fixing candidate set to reduce ratio 50%, reach desired group size (k in said method 0) needed iterations is approximately log 2(K/k 0).In practice, this needs iteration usually 1-4 time.The upper limit of the overall complexity of said procedure depends on the complexity of a K user BF (K-user BF) process being carried out to 2 wave beam vector optimization iteration.
As mentioned above, at least one embodiment, the performance index of using in the ASP process are the speed relevant to candidate user, wherein, and by best (standardized) beam vectors is calculated to maximize this speed.Can in all sorts of ways to being calculated for the maximized optimum beam vector of speed.For example, in a kind of possible method, this calculates the duality based on up link-down link.Suppose that the overall transmission power for current candidate set is P (P>0), and the current size of this group is k.Current power vector for candidate set is p=(p 1, p 2..., p k), p wherein 1+ p 2+ ...+p k=P.In one approach, can be by p ibe set to equal P/k.Vector h ibe for user i (i=1 ..., n k) dimension channel vector.Can by as get off to maximize speed.At first use following equation calculating parameter S:
S=I nxn+ ∑ 1≤j≤kp jh jh j *(equation 1)
Wherein, I nxnit is n * n unit matrix.Then, by calculate the S for user 1 to k as got off i:
S i=S-p ih ih i *(equation 2)
Should be noted that S ibe positive Hermitian matrix, it can realize stable inverting.Next, can by as get off to calculate the user 1 maximized up link SINR to k:
Max_uplink_SINR i=p imax_eigen_value (S i -1h ih i *) (equation 3)
Can use for example Minimum Mean Square Error (MMSE) calculating to carry out this optimization.Should be noted that
S＝I+H·D·H *
Wherein, H is n * k matrix, and its j row are h j; And D is the diagonal matrix of k * k, wherein D=diag (p 1..., p k).
In the situation that do not consider QoS, above-mentioned ASP process can be used for finding out user's subgroup and shares the every sub-channels in the OFDMA system.In the following discussion, this concept is expanded, in order to provide an excited users group in each of a plurality of parallel channels when considering QoS.This process is called the prediction of activation group frame by frame (FW-ASP) process.Provide QoS to mean: minimum and the maximum every frame rate special to each user assignment retrain.The FW-ASP process is a kind of iterative program of low complex degree, and it,, for selecting the user's activation group on every sub-channels, wherein, can realize relatively high spectrum efficiency on subchannel.As next described in more detail, FW-ASP can provide the activation group that reaches or at least approach the relevant every frame rate of minimum for user's QoS.As aforesaid ASP process, can before the BF optimizing process, by the FW-ASP process, reduce significantly its computation complexity.In at least one embodiment, the FW-ASP process also provides power division, beam vectors, may also have initial weight to follow-up BF optimizing process, further reduces the optimization complexity.
Fig. 4 is according to embodiments of the invention, shows the flow chart of selecting the illustrative methods 60 of a plurality of excited users group for a plurality of parallel channels in communication network.Method 60 means a kind of may the realization of FW-ASP process.Can be in realizing the network based on OFDMA of SDMA using method 60 carry out BF optimize before the initial set of chooser channel.Also there is other application.With reference now to Fig. 4,, in the situation that do not consider QoS, at first method 60 selects the little user's subgroup (square frame 62) that may have high-throughput for every sub-channels in the OFDMA network.In every sub-channels, can use aforementioned ASP process (for example, the method 40 of Fig. 3) to carry out this subgroup selects.After having selected subgroup, calculate every frame rate parameter (square frame 64) of each user.Word " frame " refers to single OFDMA symbol, comprises all subchannels.By the speed addition of certain user by all subchannels, calculate every frame rate of this user, wherein, all subchannels all comprise this user in their activation group.
Next, increase than by one or more user, being distributed the relevant every frame rate of minimum of QoS obtained to retrain little power (may also have priority weighting) (square frame 66).This increase can be the form according to predetermined increment size.This increase is intended to increase every frame rate of user, thereby makes this speed at least approach least commitment.Then, reduce than by one or more user, being distributed the relevant every frame rate of minimum of QoS obtained to retrain large power (may also have priority weighting) (square frame 68).In at least one embodiment, the power reduction equals previous increased power amount, thereby makes gross power keep identical.Reduce every frame rate that power will reduce the user most probably, but this speed can not reduced under minimum every frame rate constraint.If do not have the user to distribute the constraint of the every frame rate of the maximum obtained higher than them, can use so and there are the most one or more users of high every frame rate.In at least one embodiment, increase the power of unique user in square frame 66, reduce the power of unique user in square frame 68.Weight (the w of above indication k) be for being reflected in the value of resource each User Priority between allotment period.Can revise or not revise these weights during the FW-ASP process.In at least one embodiment, the scheduling mechanism by higher level provides initial weight.Now, can enlarge the candidate set (square frame 70) for some subchannels by increase one or more users that reject before (that is the user who, rejects) between initial subgroup selecting period.
Next can determine: whether all candidate set are current all has desired activation group size (square frame 72).If not, method 60 can be got back to square frame 62 so, and by candidate set, the power division of latest definition, may also have weight, repeat this process (square frame 72-N).If all candidate set all have a desired activation group size (square frame 72-Y) current, so next can determine: whether all users are equal to or higher than (or at least one embodiment enough close to) minimum every frame rate constraint (square frame 74).If not, so can be from square frame 62, by candidate set, the power division of latest definition, may also have weight, carry out repetition methods 60 (square frame 74-N).If all users at least approach minimum every frame rate constraint, method 60 can finish (square frame 76) so.If carry out in square frame 62 for the subgroup of every sub-channels and select by the method 40 of Fig. 3, so after first iteration, the square frame 42 and 44 that the new iteration of each of method 60 can skipping method 40.
As previously mentioned, after a plurality of subchannels are selected to the initial activation group, can carry out combined optimization to scheduling and physical wave beam shaping.This optimization is attempted to maximize throughput frame by frame under the restriction of the rate constraint frame by frame relevant at QoS.In at least one embodiment, be scheduled to the user of every sub-channels by above-mentioned FW-ASP process, to reduce complexity.The FW-ASP process can transmit that the initial activation component be joined to the BF optimizing process, power level, beam vectors may also have weight.In at least one embodiment, BF optimization is to change at power the iterative process replaced between (power-shift) iteration and beam vectors iteration.For given power division frame by frame, the beam vectors iteration attempts to find out the optimum beam vector.Power is adjusted iteration and is attempted power for example, is changed towards the power that makes the parameter that speed is relevant (, weighted sum rate (WSR, weighted-sum rate) etc.) produce the user/subchannel of highest-gain.In one approach, carry out a beam vectors iteration (but also can use other method) every power iteration repeatedly.Each beam vectors iteration can be inputted the existing power division (p of each user in every sub-channels ik) and channel condition information (CSI).Can the part of CSI as self-contained process will be generated.The beam vectors iteration is intended to optimize the beam vectors of excited users, and therefore optimizes the speed of these users in all subchannels.
In the following description, according to every frame rate constraint of the every frame rate to the user and QoS defined, compare, with proprietary term, the user is classified.For example,, if every frame rate of user (that is, R between minimum and maximum every frame rate constraint max, k>=R k>=R min, k), this user is called to " being met ".If every frame rate of user is less than minimum every frame rate constraint (that is, R k<R min, k), this user is called to " speed is too low ".Finally, if every frame rate of user is greater than maximum every frame rate constraint (that is, R k>R max, k), this user is called to " speed is too high ".
Each power iteration is intended to improve the too low user's of interior at least one speed of following subchannel power level, and wherein, this subchannel will make the parameter that throughput is relevant (for example, weighted sum rate (WSR)) produce highest-gain.If there is no the too low user of speed, can use one or more users that are met so.In a method, can increase to the user in respective sub-channel predetermined power increment value.Then reduce the power of same amount in too low user at least one speed, this user will make the parameter decrease that throughput is relevant minimum.After each power iteration, gross power should remain unchanged.If there is no the too low user of speed, can use one or more users that are met so.Usually, in the current power iteration of following subchannel, without carrying out throughput gain and reducing and calculate, wherein, the power division of this subchannel does not change in power iteration before.Similarly, each BF iteration can be skipped from last BF iteration and start not by the subchannel of power iterative modifications.
Fig. 5 and 6, according to embodiments of the invention, shows the part of the flow chart of the illustrative methods 80 for carrying out beam forming optimization.Method 80 is to can be used for the beam forming of network's coverage area and the iterative program of scheduled for executing combined optimization.With reference to figure 5, every kind of combination for user and subchannel in the initial activation group, at first obtain power (p ik), channel (h ik) and beam vectors (v ik) information (square frame 82).As previously mentioned, can provide the initial activation group with FW-ASP.The FW-ASP process can also generate initial power information (p ik) and initial beam vector information (v ik), wherein i is sub-channel index, k is user index.Can receive initial channel information (h from channel estimator or some other sources ik).Can obtain each user's weight information w simultaneously k(square frame 84).Then can calculate each user's speed frame by frame (square frame 86).As previously mentioned, user's speed frame by frame be this user in all following subchannels speed and, wherein, this user is in the activation group of these subchannels.Due to the duality of up link and down link, provide the speed (wherein, k ∈ A (i) and A (i) are the activation groups of subchannel i) of user k in subchannel i by the up link expression formula:
R ik＝log(1+a ikkp ik/(1+∑ j∈A(i)，j≠ka ikj·p ij))
Wherein, a ikj≡ | v ikh * ij| 2.The speed frame by frame of user k can be expressed as:
R k＝∑ i，k∈A(i)R ik
After definite speed frame by frame, next determine that each user is met, speed is too low or speed too high (square frame 88).
With reference now to Fig. 6,, next can carry out initial power and change iteration (square frame 90).As mentioned above, during power changes iteration, increase the power level of at least one user in particular sub-channel.Selected at least one user/subchannel combinations refers to increases a kind of combination (or multiple combination) that power can make the parameter generating highest-gain that throughput is relevant.If there is the too low user of speed, select the too low user of speed; If the user that neither one speed is too low, select the user who is met so.During power changes iteration, the power level of a user/subchannel will be reduced by least in addition.Total power reduces will equal performed total increased power before, thereby change iteration for power, and total power is changed to 0.Selectedly at least one the user/subchannel that reduces power, refer to that reducing power makes the minimum a kind of combination (or multiple combination) of parameter decrease that throughput is relevant.
For as above-mentionedly increase and reduce power, can use predetermined power amount Δ as the increment/decrement value.In at least one embodiment of the present invention, when the power iteration " stops ", power amount Δ can be reduced to a constant percentage.Same user in same subchannel during same iteration increases and while deducting power amount Δ, the power iteration stopping.Can also use in these cases other technology for reducing power amount Δ.
In at least one embodiment of the present invention, the relevant parameter of throughput of using during power transformation iteration is to use aforementioned priority weighting w ikthe weighted sum rate frame by frame (WSR) calculated.For subchannel i, weighted sum rate can be expressed as:
WSR i＝WSR i(p i)＝∑ k，k∈A(i)w kR ik
Then can be calculated as by " frame by frame " WSR:
WSR＝∑ i＝1:NWSR i
During power changes iteration, for the every kind of combination that there is and do not have excited users and the subchannel of power increment, can calculate this parameter.Then, maximized one or more combinations of gain that can select to make WSR are with for increasing power.Can be by following calculated gains:
G ik(Δ)≡WSR i(p’ i)-WSR i(p i)
Wherein, G ikgain, p ' ipass through p ik→ p ik+ Δ is from p iobtain.Then, can reduce power by identical method.Then, can select to make the minimized a kind of and multiple excited users/subchannel combinations of the minimizing of WSR with for reducing power.Should be noted that, change in iteration at follow-up power, only need to upgrade the yield value calculated and minimizing value for the subchannel of having revised in the current power iteration.
After completing power transformation iteration, next can determine whether to have met the predetermined condition (square frame 92) relevant to power transformation iteration.In at least one embodiment, this condition can be checked to determine that the power of for example whether having carried out pre-determined number changes iteration.Can also use other condition.If do not meet this condition (square frame 92-N), method can be returned to square frame 86 so, recalculates each user's that power level changed speed frame by frame at square frame 86.Then, can in square frame 88, to these users, reclassify, then can in square frame 90, carry out another power and change iteration.Can repeat this order until meet this condition (square frame 92-Y).When meeting this condition, next can carry out beam vectors Optimized Iterative (square frame 94).The beam vectors Optimized Iterative can utilize for example, with above-mentioned and ASP process (, seeing above equation 1,2 and 3) relevant for making the similar technology of the maximized optimum beam vector calculation of speed.After this is processed, for i=i:k, by as the compute beam vector that gets off:
v i＝eigen_vector_of_max_eigen_value(S i -1·h i·h i *)
Usually only need to process the subchannel of having revised in power before changes iteration in the beam vectors Optimized Iterative.
After completing the beam vectors iteration, can determine whether to meet second condition (square frame 96).Second condition will determine when method 80 finishes.Second condition requires the power of for example before method 80 finishes, carrying out pre-determined number to change iteration.In another method, second condition requires all users before method 80 finishes to become " being met " user.Can also use polynary condition.For example, although second condition has been specified the beam vectors iterations of the maximum allowed before the end,, if all users become " being met " user or better user before reaching maximum times, can finish ground more early.Can also use other condition.When finally meeting this condition, method 80 finishes (square frame 98).
Fig. 7, according to embodiments of the invention, shows the block diagram of exemplary base 100.As shown, base station 100 comprises: OFDMA/SDMA transceiver 102, controller 104 and channels determining unit 106.OFDMA/SDMA transceiver 102 can be coupled to the signal of a plurality of antennas 108 to help sending and receiving to and from wireless medium.OFDMA/SDMA transceiver 102 is multi-user's transceivers, and it can be a plurality of user's services in 100 overlay area, base station simultaneously.Controller 104 can comprise scheduler function body 110, for carrying out the OFDMA scheduler task of base station 100.Channels determining unit 106 can be used for determining the channel information of the various channels of being served by base station 100.Channels determining unit 106 can comprise the channel estimation function body of the channel estimating for calculating various channels, and/or channels determining unit 106 can receive and be organized in the channel information that other places generate.
In at least one embodiment, controller 104 communicates in efficient mode on frequency spectrum the parameter of being used with the user of 100 overlay area, base station for determining by OFDMA/SDMA transceiver 102.For example, controller 104 can identify to OFDMA/SDMA transceiver 102 the excited users group of each available subchannels.Controller 104 can also be determined the power information p that OFDMA/SDMA transceiver 102 will be used ikwith optimum beam shaping vector v ik.Then, OFDMA/SDMA transceiver 102 can be used special-purpose power level and beam vectors, to or user from suitable subchannel send or receive data.Frame ground upgrades this information one by one.In at least one embodiment of the present invention, controller 104 can use the beam forming of iteration and scheduler program (for example, Fig. 5 and 6 method 80) to generate the information of being used by transceiver 102.Controller 104 can also use activation group as above prediction (ASP) process and/or the prediction of activation group frame by frame (FW-ASP) process to generate initial activation group and out of Memory with the beam forming for iteration and scheduler program.
In the above-described embodiments, novel technology described in user in the respective coverage areas territory context of being served in base station in to the wireless network based on OFDMA.Should be appreciated that these technology can also carry out for a plurality of parallel channels via single source and a plurality of remote entity other application of radio communication.
Can realize technology of the present invention and structure by various form.For example, feature of the present invention can be embodied in base station, WAP (wireless access point), communication satellite, network interface unit (NIC) and other network interface structure, integrated circuit, can be presented as the instruction and/or the data structure that are stored on machine readable media, and/or be presented as other form.The available example of dissimilar machine readable media comprises floppy disk, hard disk, CD, compact disk read-only memory (CD-ROM), digital video disc (DVD), Blu-ray disc, magneto optical disk, read-only memory (ROM), random asccess memory (RAM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), magnetic or optical card, flash memory and/or is applicable to the medium of other type of store electrons instruction or data.
In at least one embodiment, two or more square frames in block diagram can be implemented as the software in single (or a plurality of) digital processing device.For example, the digital processing device can comprise that general processor, digital processing unit (DSP), Reduced Instruction Set Computer (RISC), complex instruction set computer (CISC) (CISC), field programmable gate array (FPGA), application-specific integrated circuit (ASIC) (ASIC) and/or other comprise the device of above combination.Can combine to realize with hardware, software, firmware and its.For example, term as used herein " logic " can comprise the combination of software or hardware and/or software and hardware.
In aforesaid detailed description, for simplifying purpose of the present invention, by various Feature Combinations of the present invention in one or more independent embodiment.Disclosed method should not be construed as following intention: claimed invention need to be than the clear and definite feature of statement many feature also in claim.Definite, as claim is reflected, aspect of the present invention has the feature fewer than all features of each disclosed embodiment.
Although described the present invention in conjunction with specific embodiment, should be appreciated that under the condition that does not break away from the spirit and scope of the present invention, those of ordinary skill in the art can modify and be out of shape embodiment.This modification and distortion are regarded as in the scope of the present invention and claim.

Claims (20)

1. one kind for supporting the method for space division multiple access access transmission, comprising:
For each of a plurality of subchannels in the orthogonal frequency division multiplex OFDM frequency band, the little excited users group with high-throughput potential be operated in base station coverage area is identified, wherein, each little excited users group is shared corresponding subchannel by space division multiple access access SDMA technology;
After described little excited users group is identified, carry out power adjustment and beam vectors optimization in the mode of iteration for the excited users in described little group, wherein, described power adjustment is for increasing the power relevant to one or more excited users and the minimizing power relevant with one or more other excited users, thereby enhanced quality-of-service QoS compliance, described beam vectors optimization is for optimizing the beam vectors relevant to the subchannel that is subject to described power adjustment impact
Wherein, excited users in described little group is carried out to the power adjustment and beam vectors optimization comprises: for each beam vectors Optimized Iterative, carry out repeatedly power and adjust iteration, wherein, each power is adjusted iteration increases and power and a minimizing and the power that excited users is relevant that excited users is relevant.
2. the method for claim 1, wherein:
Little excited users group is identified and is comprised:
At first all users in described base station coverage area are appointed as to the candidate user of the first subchannel in the OFDMA bandwidth;
Calculate the performance index of each candidate user relevant to described the first subchannel;
Performance index based on calculated, reduce the quantity of the candidate user relevant to described the first subchannel.
3. method as claimed in claim 2, wherein:
Little excited users group is also identified and comprised: the mode with iteration repeats to calculate and reduce, until reach desired candidate user quantity.
4. method as claimed in claim 3, wherein:
The quantity that reduces described candidate user comprises: under the prerequisite of the candidate user quantity that is not less than described expectation, reject the described candidate user of predetermined percentage during each iteration.
5. the method for claim 1, wherein:
Little excited users group is identified and comprised: identified making each user can at least approach by the little excited users group of every sub-channels of the every frame rate of minimum of service quality QoS constraint defined.
6. the method for claim 1, wherein:
Little excited users group is identified and is comprised:
According to the mode of not considering service quality QoS, select user's subgroup of every sub-channels;
Calculate every frame rate of each user;
One or more users' that the every frame rate of the minimum that increase is more relevant than QoS is low power;
One or more users' that the every frame rate of the maximum that minimizing is more relevant than QoS is high power;
Wherein, the recruitment of power is substantially equal to the reduction of power.
7. method as claimed in claim 6, wherein:
Little excited users group is identified and is comprised:
Every frame rate of each user of double counting;
Increase one or more users' power and the one or more users' of minimizing power, until all users at least approach the every frame rate of minimum that described QoS is relevant.
8. the method for claim 1, wherein:
Excited users in described little group is carried out to the power adjustment and beam vectors optimization comprises:
Calculate the speed frame by frame of each excited users;
Determine too low user or the too high user of speed of user, speed that each excited users is met;
Wherein, if there is the too low user of speed, each power is adjusted iteration increases the user-dependent power too low with described speed; If there is the too high user of speed, each power is adjusted the user-dependent power that iteration reduces and described speed is too high.
9. the method for claim 1, wherein:
Each power is adjusted iteration based on making weighted sum rate WSR produce the excited users of highest-gain and the excited users that subchannel selects to increase power when increasing power.
10. method as claimed in claim 9, wherein:
Each power is adjusted iteration based on when reducing power, making the minimum excited users of weighted sum rate WSR decrease and subchannel select to reduce the excited users of power.
11. the device for supporting that the space division multiple access access is transmitted comprises:
OFDM OFDMA space division multiple access SDMA transceiver, for:
Send data and receive data from a plurality of users to a plurality of users via a plurality of OFDMA subchannels, wherein, a plurality of users can use the SDMA technology to share every sub-channels simultaneously, and described OFDMASDMA transceiver is connected to a plurality of antennas;
Controller, it comprises scheduling feature, described scheduling feature is used for:
Dynamically, to the beam forming data of subchannel distributing user and definite each user/subchannel, described controller has:
Recognition logic, for: for a plurality of subchannels of orthogonal frequency division multiplex OFDM frequency band each, the little excited users group with high-throughput potential is identified, wherein, each little excited users group is shared corresponding subchannel;
Actuating logic, be used for: after described little excited users group is identified, carry out power adjustment and beam vectors optimization in the mode of iteration for the excited users in described little group, wherein, described power adjustment is for increasing the power relevant to one or more excited users and the minimizing power relevant with one or more other excited users, thereby enhanced quality-of-service QoS compliance, described beam vectors optimization is for optimizing the beam vectors relevant to the subchannel that is subject to described power adjustment impact
Wherein, the described actuating logic that carries out power adjustment and beam vectors optimization for the excited users to described little group comprises: for for each beam vectors Optimized Iterative, carry out repeatedly power and adjust the logic of iteration, wherein, each power is adjusted iteration increases and power and a minimizing and the power that excited users is relevant that excited users is relevant.
12. device as claimed in claim 11, wherein:
The described actuating logic that carries out power adjustment and beam vectors optimization for the excited users to described little group comprises:
For calculating the logic of speed frame by frame of each excited users;
The user's that the user that user, the speed be met for definite each excited users is too low or speed are too high logic;
Wherein, if there is the too low user of speed, each power is adjusted iteration increases the user-dependent power too low with described speed; If there is the too high user of speed, each power is adjusted the user-dependent power that iteration reduces and described speed is too high.
13. device as claimed in claim 11, wherein:
Each power is adjusted iteration based on making weighted sum rate WSR produce the excited users of highest-gain and the excited users that subchannel selects to increase power when increasing power.
14. device as claimed in claim 13, wherein:
Each power is adjusted iteration based on when reducing power, making the minimum excited users of weighted sum rate WSR decrease and subchannel select to reduce the excited users of power.
15. the goods for supporting that the space division multiple access access is transmitted comprise:
Be used for each for a plurality of subchannels of orthogonal frequency division multiplex OFDM frequency band, the module that the little excited users group with high-throughput potential be operated in base station coverage area is identified, wherein, each little excited users group is shared corresponding subchannel by space division multiple access access SDMA technology;
For after described little excited users group is identified, carry out for the excited users in described little group the module that power adjustment and beam vectors are optimized in the mode of iteration, wherein, described power adjustment is for increasing the power relevant to one or more excited users and the minimizing power relevant with one or more other excited users, thereby enhanced quality-of-service QoS compliance, described beam vectors optimization is for optimizing the beam vectors relevant to the subchannel that is subject to described power adjustment impact
Wherein, described module of for the excited users to described little group, carrying out power adjustment and beam vectors optimization comprises: for for each beam vectors Optimized Iterative, carry out repeatedly power and adjust the module of iteration, wherein, each power is adjusted iteration increases and power and a minimizing and the power that excited users is relevant that excited users is relevant.
16. goods as claimed in claim 15, wherein:
Described module of for the excited users to described little group, carrying out power adjustment and beam vectors optimization comprises:
Each power is adjusted the module that the excited users of iteration based on will make weighted sum rate WSR generation highest-gain when increasing power and subchannel select to increase the excited users of power.
17. the article of claim 16, wherein:
Described module of for the excited users to described little group, carrying out power adjustment and beam vectors optimization comprises:
Each power is adjusted the module of iteration based on making the minimum excited users of weighted sum rate WSR decrease and subchannel select will to reduce the excited users of power when the minimizing power.
18. the system for supporting that the space division multiple access access is transmitted comprises:
OFDM OFDMA space division multiple access SDMA transceiver, for:
Send data and receive data from a plurality of users to a plurality of users via a plurality of OFDMA subchannels, wherein, a plurality of users can use the SDMA technology to share every sub-channels simultaneously;
Be coupled to a plurality of dipole antennas of described OFDMA SDMA transceiver, it contributes to the sending and receiving of wireless signal;
Controller, it comprises scheduling feature, described scheduling feature is used for:
Dynamically, to the beam forming data of subchannel distributing user and definite each user/subchannel, described controller has:
Recognition logic, for: for a plurality of subchannels of orthogonal frequency division multiplex OFDM frequency band each, the little excited users group with high-throughput potential is identified, wherein, each little excited users group is shared corresponding subchannel;
Actuating logic, for: after described little excited users group is identified, with the side of iteration
Formula is carried out power adjustment and beam vectors optimization for the excited users in described little group, wherein,
Described power adjustment for increasing the power relevant to one or more excited users and reduce and
The relevant power of one or more other excited users, thereby enhanced quality-of-service QoS compliance,
Described beam vectors optimization is relevant to the subchannel that is subject to described power adjustment impact for optimizing
Beam vectors,
Wherein, the described actuating logic that carries out power adjustment and beam vectors optimization for the excited users to described little group comprises: for for each beam vectors Optimized Iterative, carry out repeatedly power and adjust the logic of iteration, wherein, each power is adjusted iteration increases and power and a minimizing and the power that excited users is relevant that excited users is relevant.
19. system as claimed in claim 18, wherein:
Each power is adjusted the excited users of iteration based on will make weighted sum rate WSR generation highest-gain when increasing power and subchannel and is selected excited users with for increasing power.
20. system as claimed in claim 19, wherein:
Each power is adjusted iteration based on making when the minimizing power the minimum excited users of weighted sum rate WSR decrease and subchannel select excited users with for reducing power.
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